Radio system



F. B. FALKNOR RADIO SYSTEM Jan. 8, 1929. v 1,698,014

Filed March 15, 1924 INVENTOR WITNESSES:

. Fran/r B. Fal/mar WN v BY I 7 AT'EORNEY UNITED FFICJE.

FRANK B. FALKNOR, WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY,

VANIA.

RADIO SYSTEM.

Application filed March 13, 1924; Serial No. 698,928.

My invention relates to radio systems and particularly to apparatus for the reception of radio signals.

One object of my invention is to provide means whereby radio signals can be received and maintained at a volume.

Another object of my invention is to provide means for automatically adjusting the regenerative function CII'CIllt'lIl response to tude of the received energy from a radio sending apparatus for the ing for such changes.

In the art of the reception of radio signals,

a phenomenon known encountered. This phenomenon consists of a Th cyclic falling off andincrease in strength of signals received by a gi other given station when the signals sent out are of constant energy. The phenomenon appears to be due to ch of the radio frequency surface of the earth.

mined whether the falling off is due to refraction through clouds, reflection from layers of varying density of air, or to someas yet unsuggested influence.

The efi'ect of fading is to produce a. rather troublesome loss of signal energy at a rethis loss occurring at inter from a small number of minutes to a number of hours.

invention provides means for overcomding upon the received signals. My apparatus is to be applied to a regenerative radio receiver, preferably of the p aerial and a regenerative feed-back, and consists of apparatus for ceiving station, vals WhlCh vary y ing the effect of fa type embodying a 100 varying the amount duced signal energy.

changes in signal one other radio receiver.

tion. 1 11, he g irea 1n response to changes in received This result is secured by adjusting the value of a resistive shunt about the regenerative feed-back coil in response to of a regenerative A parallel condenser substantially constant desired signals.

former feeding radio recelvlng is connected si in the magniin a changes denser 11 to circuit feature.

purpose of compensat- The A CORPORATION OF PENNSYL- to tune the loop COD- primary Winding of feed-back coupling transformer 5 is also conas fading has been the customary plate y device fu ven station from anode 22 through leak 24. An ange in the absorption former 25 is a as it travels across the It is, as yet, undeterplate circuit of pling resistance denser 28; The

A fourth triode 31 its grid and filament the primary 0 transformer 5.

of regeneration pro- Triodes 2, 8,

means, as indicated.

In the, operation rgy picked up by anadjust the the oscillating circuit, from the followof my device, triodes 2 and 8, thereby placing circuit in condition for operation. Ithen condenser 6 to bring the tuning of the condenser 6 and th transformer 5, to resonance with the desired signals. Upon the arrival of signals, they this ci triode 2 and 1ts associated circuits, amplinected in the plate circuit of the triode 2 as is potential supply 12.

is comprises the signal circuit.

rther contains a second loo antenna 21 which is connected to a third tria grid condenser 28 oscillation feed-b lso connected in the antenna circuit as well as a tuning condenser 26. The the triode 22 contains a cow 27 shunted by a by-pass conprimary Winding of the oscillation feed-back transformer 25. is also con nected in the plate circuit of triode 22. A source of plate potential 29 is likewise connected in the plate circuit. p

which is provided, has connected to the terminals of thecoupling resistor 27 and has its plate and filament connected in shunt across f the regenerative coupling The plate circuit of the triode 31 contains also a plate tuning inductance 32 and the customary source of plate voltage 33. This comprises the regulating circuit. 22 and 31 customary, with filament heating and control and a grid ack transare provided, as

I energize the signal comprising the loop 1, e secondary coil of rcuit, detected by the fie d by triode Sand perceived by the operator aerial l is connected to through signal receiver 9,

a detector triode 2 through a'grid condenser 3 and a grid leak 4, and through the grid coil coupling transformer 5.

6 serves aerial 1 to resonance at the frequency of the The plate circuit of the triode 2'contains an output circuit device 7 indicated in the sketch as an amplifying transan amplifier triode 8, to which gnal receiver 9. The output coil in the plate circuit is shunted by a provide for the regenerative I then adjust the coupling between the coils of transformer 5 to give maximum regeneration. This ener izes the signal circuit with signal energy, w ich, however, is subject to variation in strength due to fading of the received signal energy. To compensate for this fading, I then energize the triodes 22 and 31, adjust the condenser 26 for a radio frequency and increase the coupling between the primary and secondary coils of oscillation coupling transformer 25 until the circuit is set into oscillation at a frequency which gives a beat note with the radio frequency energy of the incoming signals. This beat note is adjusted to be outside of therange of audibility. It varies in intensity according to the intensity of the received signals. It is detected by triode 22 through the agency of a grid condenser and a grid leak 24 which produce a 20 negative charge upon the grid of triode 22 varying in magnitude according to the inten-' sity of the received signals, thereby changing the magnitude of the plate current of triode 22 in the usual way. The change in plate current of triode 22 produces a change in voltage drop through resistor 27, which, in turn, produces a change of voltage upon the grid of triode 31, which, in its turn, changes the impedance of tube 31. Tube 31 is shunted about the plate coil of regenerative coupling transformer 5 in the signal circuit.

When a strong signal is being received, a

substantial beat note will be produced and detected in triode 22. This produces a strong negative charge upon the grid of tfiode 22 and in turn, a substantial reduction in plate current of triode 22 and allows a smaller voltage drop across resistor 27. In consequence, the grid of triode 31 is char ed to moderately great positive voltage di erence above the filament. Under this condition, the impedance of tube 31 is relatively low and it passes. current from the plate circuit of trio de 2 and since it is connected in shunt with the plate coil of oscillation coupling transformer 5 by conductors 35, it thereby causes less than maximum regeneration to be produced.

The average potential of the grid in the triode 21 depends upon the size of the condenser 23, of the resistor 24 and of the impressed alternating potential. The alternating po 'tential impressed by the action of the coupling transformer 25 is modified by the'potential received from the loop 21. It will, therefore, vary with the strength of the signal. The output current of the triode 22 will be a direct current from the battery 29 upon which is superposed the alternating current produced by the fluctuations of the grid potential. The effect of this superposition is to alter the average value of the output current. The average potential across the resistor 27 is dependent upon the average current in the output of the triode 22. The combination of condenser 28'and resistor 27 acts as an integrating device with the result that the grid of the tube 31 has a potential corresponding to the average condition of the output circuit of the triode 22 instead of following the instantaneous values of the current in said output.

When, however, the received signals begin to fade the signal intensity received by the loop, antenna 21 results in a lower strength of beat note in the triode 22, a smaller charge on the grid of the triode 22, a greater plate current through triode 22 and a greater voltage drop across resistor 27. The greater voltage drop in resistor 27 causes the grid 0 triode 31 to become lesspositive with respect to its filament, thereby increasing the impedance of the tube, permitting less of the plate current of triode 2 to pass through triode 31 and causing more plate current to pass through the primary coil of oscillation transformer 5. The greatercurrent in this coil produces greater regeneration in the signal circuits and thereby proportionately greater signal volume with respect to the received energy. In this way, the degree of regeneration in the signal circuit is controlled by the signal intensity received upon loop aerial 21, thereby maintaining a substantially constant signal volume in signal receivers 9 in spite of fading occurring inthe received short-wavereception, such as the reception of signals at 100 meters wave length, at which wave length fading is particularly troublesome.

In practice, my invention makes it possible to maintain substantially constant signal energy. It is particularly adaptable to the reception of voice modulated signals, since it is responsive only to actual fading and it is not responsive to changes in modulation of the signal output. It thereby compensates for the fading but leaves the changes in sound volume due to modulation, unafl'ected.

While I have shown only one embodiment of my invention, it is capable of various changes and modifications Without departing from the spirit thereof. I desire, therefore, that only such limitations shall be imposed thereon as are indicated in the appended claims.

I claim as my invention:

1. A vradio signal receiving system comprising a radio receptor circuit, a radio detector, a set of regenerative circuits interlinking said receptor and said detector, and means for automatically adjusting the degree of regeneration to maintain a constantvolume of output signals, said means comprising a second radio receptor circuit, a second radio detector, a second set of interlinking circuits adapted to produce oscillations in said second detector and said second receptor, a triode resistively coupled to said second detector, and connections shunting said triode across one of said regenerative circuits.

2. A radio receivin system comprising a radio receptor, a triode radio detector, a set of connecting circuits generative coupling transformer having plate and grid coils connected in said circuits and an adjustable resistive shunt connected across the plate coil of said coupling transformer, said adjustable resistor comprising a triode thermionic discharge device, and means whereby the conductivity of said triode discharge device is controlled by incoming signals.

3. A radio receivin radio receptor, a trio e of interlinking circuits,

system comprising a radlo detector, a set a regeneratlve coupling transformer having plate and grid coils connected in said circuits, an adjustable resistive shunt connected across the plate coil therebetween, a re- 'said derived potential.

of said-coupling transformer, said adjustable resistive shunt comprising a triode thermionic discharge device, a second oscillatory radio receiver comprising a second radio receptor, interlinking oscillatory circuit, said second receiver being connected to said triode, whereby main receiving circuit is automatically maintained substantially constant whenever the amplitude of the incoming oscillations varies from so-called fading eflects.

the signal-volume output from the a second radio detector and a second 4. In a signal-receiving system, means ineluding a thermionic tube for deriving an indication from an incomingxsignal, separate means including a thermionic tube for deriving a potential proportional to the amplitude of said signal, and means whereby the' ain in said first thermionic tube is controlle 5. Ina signal-receiving system, means including a'thermionic tube for deriving an indication from an incoming signal, separate means including a thermionic tube ing a potentialthat various withthe amplitude of said signal, and means whereby the potentials applied to the grid of said first thermionic rived potential.

In testimony whereof, I have hereunto subsc'r'bed my name this 5th day of March 1924.

FRANK B. FALKNOR,

for deriv-' tube are controlled by. said do 

